Baddha Konasana (Bound angle pose) is another foundational seated posture. It requires mobility in the the hip and ankle joints. According to B.K.S. Iyengar, it is also an excellent pose for pranayama and meditation (lol! I cannot sit it in for that long)
Just mention "hip opening" in a room full of yogis and they will drool but actually start hip opening and the groan (or groins?) begin.
As in Dandasana yesterday, if you can't keep your pelvis from tilting back then sit on support. Try sitting on the corner of a folded blanket so your sit bones are supported but the thigh are not.
Start by pressing the heels together and extending the knees apart.
Then try opening the ankles by turning the souls of the feet towards the ceiling
Finally, attempt the "classic pose" grabbing the big toes. Instead of pulling the big toes up, try to extend the big toes forward and release the groins.